Unlicensed mobile access (UMA) technology provides access to global system for mobile (GSM) and general packet radio service (GPRS) mobile services over unlicensed spectrum technologies (e.g. Bluetooth, 802.11, etc.). By deploying UMA technology, service providers can enable subscribers to roam and to perform a handover between cellular networks and public and private unlicensed wireless networks using dual-mode mobile handsets. With UMA, subscribers receive a consistent user experience for their mobile voice and data services as they transition between networks.
Thus, UMA is a technology for delivering seamless mobility between GSM and wireless local area network (WLAN) access. GSM media and signaling can be tunneled over a broadband Internet protocol (IP) network. This allows converged circuit and packet services to be delivered to a converged terminal. For example, a user with a dual mode GSM UMA handset is able to receive GSM service (voice/short message service (SMS)/GPRS) when in a home environment without using the GSM radio network.
Key to the successful operation of a dual mode solution typified by UMA is the successful handover between a cell corresponding to the un-licensed mobile technology (Bluetooth, 802.11, etc) and a cell corresponding to the licensed frequencies of the public land mobile network (PLMN). A handover to a cell corresponding to unlicensed technology is generally requested by the client, e.g., based on received WLAN signal strength. Further, a trigger to handover from an unlicensed cell to a cell of a PLMN may be generated by the client, e.g., based on received WLAN signal strength, or by the network, e.g., based on metrics derived from the up-link packets. In a dual mode environment, such a handover process is fraught with additional problems and deficiencies compared to the pure cellular handover procedure. Augmenting, optimizing, or enhancing this dual mode handover process presents a significant obstacle for network operators, system designers, and component manufacturers.